In the technical field of absorbent articles, considerable efforts have been made over many years to increase the number of manufactured articles, for example babies' diapers or incontinence diapers, per unit of volume for storage and transportation. Nowadays, for example, twice as many babies' diapers are transported by truck as were transported in a similarly sized truck a number of years ago.
Thinner articles, still with a high absorption capacity, represent one of the areas that have been improved. Enhanced thinness has been achieved principally by introduction of gel-forming polymers, called superabsorbents, in increasing concentrations in the absorption cores of the absorbent articles. The articles have in this way been improved in terms of their handling both during storage and transportation. Thinner absorbent articles have also been preferred by users, and this fact has of course also prompted various manufacturers to steer developments in this direction.
Thinness has also been achieved by the fact that the articles are nowadays compressed much more than in the past. EP 0,122,042 is one example of a patent which describes how absorbent articles are compressed efficiently so as to achieve increased thinness while at the same time maintaining or even improving the absorption capacity. Specifically, EP 1,122,042 discloses compressing absorption bodies at a low moisture content in order to maintain softness and pliability despite compression to high density levels (low bulk levels).
More effective ways of packaging absorbent articles have also been developed. The absorbent articles have been packaged with ever greater compression. The most common way of introducing a stack of absorbent articles into a bag has involved use of a special gripping device, which is allowed to compress the stack of diapers and is introduced into the bag together with said diapers. The gripping device has been designed in such a way that it has been possible to remove it from the bag when the stack has been correctly positioned in the bag.
Patent application GB 2,264,278 A describes a method for effective compression of a stack, that is to say an individual packaging unit, of absorbent articles in connection with the articles being enclosed in a band-shaped wrapper. The volume of the packaging is minimized by means of a stack of folded absorbent articles being compressed together with a two-part packaging envelope of the wrapper type. Finally, the absorbent articles are locked in the compressed state by the two parts of the packaging envelope being connected to one another when the absorbent articles are still under external compression.
EP 0,780,325 B1 describes an improved method of configuring a packaging unit, in which the folded absorbent articles have been arranged head to tail. Configuring the articles in this way in the packaging unit permits harder compression of certain types of absorbent articles in the packaging unit. The method of forming a packaging unit in said patent works best for articles which have different amounts of absorption material, that is to say different thicknesses, at their waist areas compared with the thickness at their crotch areas, which situation is relatively common. The differences in thickness between waist area and crotch area are compensated by the fact that the packaging unit has the same number of waist areas as crotch areas at the opposite surfaces in the packaging unit. The end result is a packaging unit which has uniform thickness at its opposite surfaces where the crotch areas and waist areas of the absorbent articles are alternately arranged. The packaging unit can thus be compressed and acquires increased density in, for example, a bag, without the bag having a parallel trapezoid shape.
A problem which is only partially solved in EP 0,780,325 B1 is that of protecting the folded areas at the crotch areas of the articles when the packaging unit is compressed.
When a packaging unit comprising absorbent articles folded once about a substantially transverse fold line is compressed at right angles to the material layers, the fold area is the most sensitive area of the article. High compression often means that permanent fold notches are formed, and the absorbent article will then have a hard and uncomfortable crease when it is being worn by a user. Fold notches also function as channels in which liquid can run, a fact which is particularly unfortunate when the channels extend in the transverse direction of the absorbent article and are located in the area where various body fluids such as urine are collected in the absorbent article.
Compression of other parts of the absorbent articles in the packaging unit, that is to say compression at right angles to the material layers, is not as problematic because no creases or the like are created. In addition, the material layers normally included in absorbent articles have a considerable capacity for recovering their original configuration when the compression ceases, as long as the compression has taken place at right angles to the material layers.
There is therefore still a need for a packaging unit in which the fold areas of the absorbent articles are better protected when the packaging unit is compressed in connection with introduction of the articles into a bag, for example, or upon compression in connection with enclosure in a wrapper.